Abstract: Transition from Passive-Margin to Foreland-Basin Subsidence in the Black Warrior Foreland Basin

Brian M. Whiting, William A. Thomas

The transition from a passive margin to a convergent margin predictably is marked by an increase in subsidence rate when thermally driven subsidence is overwhelmed by lithospheric flexural subsidence accompanying the initiation of a foreland basin. Along a mature passive margin (old, cold lithosphere), the change in subsidence rates is predictably large. In addition, diachronous thrusting is predicted to give rise to a discontinuously distributed transition in subsidence rates around the foreland basin. Using subsidence-rate curves derived from wells which penetrated to pre-rift basement, we evaluate the timing and distribution of the transition from passive margin to foreland basin in the Black Warrior basin, which is framed by the Ouachita and Appalachian thrust belts.

Rifting was initiated in the late Precambrian to Early Cambrian, and a passive margin was formed by Late Cambrian. In middle Mississippian, northeast-directed thrusting in the Ouachita thrust belt led to subsidence of the Black Warrior foreland basin, and northwest-directed Appalachian thrusting began in Early Pennsylvanian. Subsidence curves for the Black Warrior basin show three distinct components: (1) late syn-rift and early post-rift high subsidence rates, (2) a gradual decrease followed by a long (approx. 200 m.y.) period of very low subsidence rates, and (3) a marked increase in subsidence rates beginning in the middle Mississippian. The transition to foreland-basin subsidence began first (middle Mississippian) along the Ouachita thrust front, and later (middle Early Pennsylvan an) near the Appalachian thrust front. The results presented here indicate that the influence of the Appalachian thrust belt was subordinate to that of the Ouachita thrust belt in forming the Black Warrior foreland basin.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994